There is known an acoustic apparatus, such as an audio product and a home theater product, which is connected with speakers and outputs sound. When speakers are connected to such an apparatus, it is normally necessary to connect a plus (+) terminal and a minus (−) terminal to a plus terminal and a minus terminal of output terminals of the apparatus, respectively. It is called that speaker polarity is positive when the plus terminals and the minus terminals are correctly connected. In contrast, it is called that speaker polarity is negative when the plus terminals and the minus terminals are reversely connected.
When the speaker is negatively connected, the phase of the sound outputted by the speaker is reversed, and generally reproduction quality is deteriorated. Therefore, there is proposed a technique of employing a function of determining the polarity of speaker on the acoustic apparatus side. For example, Patent References 1 and 2 disclose a technique of determining polarity of speaker by outputting a reference sound signal prepared in advance from a speaker, collecting the outputted sound by a microphone and comparing the collected signal with the reference sound signal.
Practically, various kinds of speakers are connected to the acoustic apparatus according to a kind and a purpose of the acoustic apparatus. Patent References 1 and 2 do not provide a determination method particularly in consideration of kinds and/or characteristics of speakers.
Patent Reference 1: Japanese Patent Application Laid-open under No. H06-311578
Patent Reference 2: Japanese Patent No. 3480636